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Combined turbo-code/convolutional code decoder, in particular for mobile radio systems

a combination turbo-code and convolutional code technology, applied in the field of channel coding and decoding techniques, can solve the problems of large memory and high cost of individual decoder implementation

Active Publication Date: 2005-12-15
STMICROELECTRONICS INT NV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0021] The state metrics to be stored in the adaptable memory means may be a block of N2 words of b2 bits, with b2 being greater than b1, (for example b2=88 and N2=1728). The main memory means may comprise g groups of p elementary memories (p=3 for example) respectively dedicated to the g blocks of N1 words, with each elementary memory being adapted to store N2 words of b1 bits. The product may be equal to the greatest integer smaller than the ratio b2/b1, and the product pN2 may be equal or greater than N1. The additional memory may be adapted to store N2 words of b2-gpb1 bits (for example 16 bits).
[0022] The memory control means may address the adaptable memory means in the first configuration such that each block of N1 words of b1 bits is written in or read from its dedicated group of p elementary memories. Each state metric may be formed with gp elementary words of b1 bits plus an additional elementary word of b2-gpb1 bits. The memory control means may address the adaptable memory means in the second con

Problems solved by technology

The main problem of the above mentioned turbo-code and convolutional code decoders is the need for large memories.
Therefore, an implementation of individual decoders is costly.

Method used

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  • Combined turbo-code/convolutional code decoder, in particular for mobile radio systems
  • Combined turbo-code/convolutional code decoder, in particular for mobile radio systems
  • Combined turbo-code/convolutional code decoder, in particular for mobile radio systems

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Embodiment Construction

1. Encoding

1.1 General Considerations And Convolutional Encoding

[0052] Convolutional encoding is performed by calculating the modulo-2 sum of the input values of the current and / or selected previous time steps. Implementation therefore is straightforward and mainly includes a shift register and a couple of exclusive-OR gates. Through the way these are switched, different kinds of convolutional codes can be realized:

[0053] Systematic Codes: One of the output streams is equal to the input stream, which is the systematic information.

[0054] Non-Systematic Codes (NSC): Each output is a parity information. Parity information is produced by taking the modulo-2 sum of shift register entries stating the history of the encoding process.

[0055] Recursive Codes: A special parity signal is produced and fed back in conjunction with the systematic input.

[0056] Non-Recursive Codes: No such feedback loop exists.

[0057] An instance of a convolutional encoder is defined by a combination of thes...

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Abstract

A combined decoder reuses input / output RAM of a turbo-code decoding circuit as alpha-RAM or beta-RAM for a convolutional code decoding circuit. Additional operational units are used for both turbo-coding and convolutional coding. An effective harware folding scheme permits calculation of 256 states serially on 8 ACS units.

Description

FIELD OF THE INVENTION [0001] The invention relates in general to channel coding and decoding techniques, and in particular, to turbo-codes and convolutional codes. An application of the invention is directed in general to the field of wireless communication systems, and more particularly, to the CDMA systems such as the different CDMA based mobile radio systems like CDMA 2000, WCDMA (Wide Band CDMA) or the IS-95 standard. BACKGROUND OF THE INVENTION [0002] The third generation mobile radio system specifies convolutional codes and turbo-codes as channel coding techniques [3GPP, Technical Specification Group Radio Access Network; Multiplexing and channel coding (FDD); (3G TS 25.212 version 3.5.0(2000-12)), Release 1999]. [0003] In turbo-code encoders forward error correction is enabled by introducing parity bits. For turbo-codes, the original information, denoted as systematic information, is transmitted together with the parity information. The encoder for 3GPP includes two recursiv...

Claims

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Application Information

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IPC IPC(8): G06F11/10G06F11/08H03M13/29H03M13/41H04L1/00
CPCH03M13/2782H03M13/2903H03M13/2957H03M13/4107H03M13/3922H03M13/3927H03M13/3905
Inventor BERENS, FRIEDBERTKREISELMAIER, GERD
Owner STMICROELECTRONICS INT NV
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